The present invention pertains to an upper feed dog device for sewing machines which permits a machine to operate at high speed that is comparable to machines which do not utilize upper feed dogs, and with the drive elements for actuating the upper feed dog being arranged so that their operating noise is held at a substantially low level.
Sewing machines provided with upper feed dog devices are well known to those conversant in the sewing art and a number of U.S. patents show and describe such machines. For a detailed description of the teachings of such machines, attention is hereby drawn to U.S. Pat. Nos. 3,530,809 and 4,166,422. The known sewing machines equipped with upper feed dog devices are subject to certain disadvantages such as direct contact between the arm supporting the upper feed dog and the drive elements for actuating the same, resulting in the necessity of operating the machines at reduced speeds in order to maintain the operating noise at an acceptable level. Additionally, other known machines utilize spring means acting directly on the arm which carries the upper feed dog and such springs must be exceptionally long to properly perform their intended function. This creates a bulky, unattractive structure projecting beyond the normal profile of the machine and, being in operative association with the machine's work area, the added elements interfere with the ease of operating the machine.
The device according to the present invention eliminates the disadvantages of the known upper feed dog devices utilized in sewing machines of the prior art by providing such a device wherein the upper feed dog pressure is applied progressively to a workpiece and will increase in direct proportion to any variation in an increase in the thickness thereof. Additionally, machines to which the invention is applied are capable of operating at substantially greater speeds for there is no direct connection or contact between the feed dog carrier arm and the control arm for effecting its actuation.